CVA_COPY

• Source: https://www.freebasic.net/wiki/wikka.php?wakka=KeyPgCvaCopy
• Last revised: 2021-10-11

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Macro to initialize variadic argument list object variable from an already initialized variadic argument list object variable

Syntax

` cva_copy( dst_list, src_list )

`

Parameters

dst_list

destination cva_list variable to initialize

src_list

source cva_list variable to copy from

Description

Copies one cva_list type variable to another cva_list type variable. dst_list is initialized using current state of src_list

src_list must already have been initialized with a previous cva_start or cva_copy statement.

cva_copy is like a copy constructor for the a variadic argument list object and must eventually have a matching call to cva_end, which is like the destructor. After cva_end for dst_list has been called, dst_list can be reused and reinitialized with another call to cva_start or cva_copy. The cva_copy and cva_end calls must both be called in the same procedure (for cross platform compatibility).

Examples

start GeSHi

'' example of using cva_copy to create
'' a copy of the variable argument list

Sub proc CDecl(count As Integer, ... )
    Dim args1 As cva_list
    Dim args2 As cva_list

    '' first list
    cva_start( args1, count )

    '' create a copy
    cva_copy( args2, args1 )

    For i As Integer = 1 To count
        Print cva_arg( args1, Integer ), cva_arg( args2, Integer )
    Next
   
    '' clean-up
    cva_end( args2 )
    cva_end( args1 )

End Sub

proc( 4, 4000, 300, 20, 1 )

end GeSHi

start GeSHi

'' example of using cva_copy to create
'' a copy of the variable argument list
'' and pass it to another procedure

Sub vproc CDecl(count As Integer, ByRef args As cva_list )

    '' if we don't know that caller made a copy
    '' of args, it is safe to make our own copy
    '' and leave the passed in args untouched

    Dim a As cva_list
    cva_copy( a, args )

    Print "vproc"
    For i As Integer = 1 To count
        Print cva_arg( a, Integer )
    Next
   
    '' clean-up
    cva_end( a )

End Sub

Sub proc CDecl(count As Integer, ... )

    Dim args As cva_list
    cva_start( args, count )

    '' if don't know that the called procedure
    '' will make it's own copy, it is safe to
    '' make a copy here and pass that instead

    Dim tmp As cva_list
    cva_copy( tmp, args )
    vproc( count, tmp )
    cva_end( tmp )

    '' args is still valid, we can use it
    Print "proc"
    For i As Integer = 1 To count
        Print cva_arg( args, Integer )
    Next
   
    '' clean-up
    cva_end( args )

End Sub

proc( 4, 4000, 300, 20, 1 )

end GeSHi

Version

• Since fbc 1.07.0

Dialect Differences

• Not available in the -lang qb dialect unless referenced with the alias __cva_copy.

Differences from QB

• New to FreeBASIC

See also

• ... (Ellipsis)
• cva_arg
• cva_end
• cva_list
• cva_start

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